(1.) Field of the Invention
This invention relates to methods of and/or apparatus for controlling the supply of a liquid and has been particularly devised for controlling the supply of water for use in humidifying apparatus.
(2.) Description of the Prior Art
Previously, apparatus for controlling the supply of a liquid such as water to humidifying apparatus has used detectors and valves such as those disclosed in the specification of our U.S. Pat. No. 4,708,831. In that specification, a flow control device is disclosed wherein a liquid is allowed to enter a chamber in discrete drops, each drop interrupting a beam of infrared light so that the admission of each drop to the chamber is recorded by a controller. A valve comprising a spherical metallic member located on the outlet is opened by the controller when water is required to be supplied to the humidifier apparatus.
The device disclosed in U.S. Pat. No. 4,708,831 has a number of disadvantages.
Firstly, the infrared emitter and detector provide radiation across only a narrow part of the cross-section of the chamber. Therefore, if the device is mounted on an angle, rather than being mounted exactly vertically, drips of liquid entering the chamber may not interfere with the infrared radiation and not be detected.
Secondly, an indication of the flow rate, or maximum flow rate of liquid through the chamber is not provided.
Thirdly, there is no way of measuring or providing an indication of the amount of liquid which is actually in the chamber.
Fourthly, the metallic ball which acts as the valve member at the base of the chamber requires a relatively large amount of energy to move it in order to allow liquid to exit the chamber. Also, a large solenoid is required to provide the necessary magnetic flux density to move the ball.
Fifthly, the device disclosed in U.S. Pat. No. 4,708,831 does not have a non-return valve to prevent liquid flowing back into the chamber when the magnetic ball valve is opened.
It is an object of the present invention to provide methods of and/or apparatus for controlling the supply of a liquid which will at least provide the public with a useful choice.